Combined view finder and range finder



Feb. 11, 1941. c. ORT 2,231,734

COMBINED VIEW FINDER AND RANGE FINDER Original Filed ma 1, 193-7 10 are well known Patented Feb.1l, 1941 UNlTED STATES 2,231,734 COMBINED VIEW rmnaa AND RANGE FINDER Carl Ort, Stuttgart, Germany, assignor to EastmanKodak Original application 140,231. Divided and 1089, Serial No. 1936 c mpan poration of New Jersey May 1, 1931, Serial No.

Rochester, N. Y., a corthis application July 25,

286,383. In Germany July 28,

6 Claims. (Cl. sit-2.4)-

This is a division of my application Serial Number 140,231, filed May 1, 1937, now Patent No.

2,191,027, issued February 20, 1940, Figures 4, 7,

and 8 thereof being reproduced herewith as Fig- 5 ures 1, 2, and 3.

This invention relates to optical systems. It relates to optical systems which include means for deviating a ray of light.

Many devices such as prisms and glass wedges,

in the art as means for deviatins light rays. It is sometimes desirable to use some such deviating means in an optical system in which lenses are also employed. It is an object of the present invention to provide a simple opti- 5 cal light deviating device which also comprises part of the lens system with which it is used, 1. e., an optical device having variable deviating power and constant focal power.

It is a further object of the invention to provide a combination range finder and view finder employing this light deviating means and having means for coupling the light deviating means to the focusing arrangement of the camera with which it is employed and/ or means for providing I as an erect image in the view finder eye-piece when positive lenses only are employed, and/or a particularly simplified lens system which insures that the image seen in the combination view finder range finder has suificient magnification for range 30 finding purposes and also includes the correct field of view for view finding purposes.

Other objects and advantages of the invention will become apparent from the following description when read in connection with the 5 accompanying drawing in which,

Fig. 1 is a perspective view showing a portion of a camera on which is mounted a combined range and view finder incorporating the invention.

Fig. 2 shows a cross section ofa range finder of the type shown in Fig. 1 and including a very simplified and convenient device for increasing the magnification of the image seen therein (to facilitate range finding) without altering the field of view (which must be correct for view finding purpo e w Fig. 3 shows a variation of the embodiment shown in Fig. 2 wherein slight adiustment of one of the optical elements is provided to permit rela- 50 tive focusing of the two fields of the range finder.

According to the invention, a range finder is provided as shown in Fig. 1 having a simplified light deviating means. The arrangement shown is a combination view finder range finder wherein 55 the direct beam of the range finder wholly constitutes the view finder field, and wherein the range finder light deviating means is coupled to the camera focusing adiustor. However, it is to be understood that this light deviating means may be incorporated in many various types of range finders without departing from the spirit of the invention. g

This perspective drawing (Fig. 1) shows part of a camera housing 0 upon which is mounted a range finder 4i whose housing has been partly broken away to show the optical components therein which include two front windows 41 and 43 fortransmitting the indirect and direct beams respectively and a rear window or eyepiece In a well-known manner, the indirect beam is reflected by a fixed reflector 45 through a light deviating'device 41 to a semi-transparent mirror 46 which reflects it to the eye-piece ll. The direct beanr coming through the window 43 passes through a dispersive lens .50 to the eyepiece and aportion of this beam passes through the semi-transparent mirror 48. In accordance with the invention, the light deviating means ll comprises a planoconcave lens pivotally mounted at 41' to be rotatable about a line through the center of curvature of this surface.

This divisional application is primarily concerned with the view finder comprising the lens 50 and the eye-piece 44.

The combination range finder view finder shown in Fig. 1 has as a view finder, an inverted Galilean telescope. The reflected beam of the range finder also traverses an inverted Galilean telescope I wherein the front negative component also con-. stitutes wholly the ray reflecting means.

In a combination view-finder-range-finder of this type there are two requirements which are somewhat conflicting. For range finding purposes it. is usually desirable to have as high a magnificationas possible. For view finding purposes, it is necessary that the total field of view included be approximately that which is to be photographed. In most optical systems the field of view decreases when the magnification increases.

According to the invention there is provided a simple and satisfactory form of wide angle, high magnification, system as shown in Figs. 2 and 3. I have found that satisfactory magnification for range finding purposes may be obtained (while the angle, marked V in the figure, which defines the field of view is maintained constant) by using a thick plane-concave lens 10 for the front element of the view finder. It will be apparent to those skilled in the art that the magnification factor increases, i. e. approaches unity, as the distance between the concave surface of the element I0 approaches the convex surface of the eye-piece 44, that is, as the value A becomes smaller. As is well known, the power of the concave surface of the element 10 must become less as the value A decreases if the combination of the components 10 and 44 is to form an inverted Galilean telescope at all times. However, in this embodiment of the invention, a thick lens I! is used decreasing the value A (l. e. giving higher magnification) but maintaining the field of view as defined by the angle unchanged. Hence, the optical system serves satisfactorily asa view finder. The distance between the front plano surface of the component 10 and the rear plano surface of the eye-piece component M is designated as L. I have found that a system in which the ratio of A to L is between .5 and .75 gives the most satisfactory results.

Since in view finders of this general type, the eyepiece has negligible thickness, i. e. as shown in Fig. 2, is less than i or even 39 of the overall length of the view finder, the above limits for the ratio of A to L, mean that the thickness of the front negative element must be between and 1 times the spacing A. That is, A must be between 1 and 3 times the thickness of the front element 10.

ing the range finder housing 4| very high indeed.

Thus my invention provides a simple means for avoiding a cumbersome range finder arrangement.

A similar arrangement is shown in Fig. 3 wherein the plano-concave component 10 is divided into two elements, a plano disk 12 and a plano concave element I3. The plane disk 12 may constitute the front window of the range finder and the plano concave element 13 is made adjustable axially to focus one half of the range finder field relative to the other half, 1. e. to adjust the manification of the view finder to match that of the other half of the range finder.

As far as the present invention is concerned, the thickness of the disk 12 may be considered as added to that of the element 13 and the spacing therebetween as added to the spacing between the elements 44 and 13, i. e. added to the spacing A.

It is to be understood that any of the lens components in the optical systems shown may, in most cases, be compound to correct for optical aberration if so desired.

Having thus described the invention, I wish to point out that it is not confined to the specific structures and applications shown but is of the scope of the appended claims.

What I claim and wish to protect by Letters Patent of the United States is:

1. A view finder for cameras consisting of a thin plano convex element as an eye-piece and a. relatively thick concave plano front element spaced from the eye-piece a distance between .5 and .75 of the axial length of the view finder, said distance being between one and three times the axial thickness of said front element, the plano surfaces being outward, whereby the finder has simultaneously, a small cross section compared to its length, a high covering power and a magnifying power difi'ering from unity by a relatively small amount.

2. A view finder for cameras consisting of a thin positive element as an eye-piece, a thick negative front element spaced from the eye-piece a distance between one and three times the axial thickness of the front element, all refractive surfaces of the elements being surfaces of revolution about the optic axis of the finder, and a field defining means adjacent to the front element having a rectangular aperture concentric with said optic axis.

3. A view finder for cameras consisting of a thin positive element as an eye-piece, a thick negative front element spaced from the eye-piece a distance equal to about twice the axial thickness of the front element. all refractive surfaces of the elements being surfaces of revolution about the optic axis of the finder, and a field defining means adjacent to the front element having a rectangular aperture concentric with said optic axis.

4. A range finder of the coincidence type employing two optical systems having a thin positive lens as a common eye-piece, one of the systems forming a view finder and consisting of this eye-piece, a thick negative lens spaced in front of the eye-piece a distance between one-half and three-quarters of the overall axial length of said one of the systems, said distance being betweenone and three times the axial thickness of said negative lens and the refractive surfaces of the eye piece and negative lens being surfaces of revolution about the optic axis of the view finder system, and a field defining means adjacent to said negative lens having a rectangular aperture concentric with said optic axis.

5. A range finder according to claim 4 in which the negative lens is a plano concave element and the positive lens is a convex plano element, the plano surfaces being turned outward.

6. A range finder according to claim 4 in which the negative lens is axially adjustable to adjust the magnification of the view finder.

CARL ORT. 

